Liquid crystal composition and liquid crystal display element

ABSTRACT

Disclosed are: a liquid crystal composition which satisfies at least one property selected from the properties including a high upper-limit temperature of a nematic phase, a low lower-limit temperature of a nematic phase, a low viscosity, high optical anisotropy, high positive dielectric anisotropy, a high specific resistance, high stability toward ultraviolet ray and high stability toward heat or has a proper balance between at least two properties selected from the aforementioned properties. Specifically disclosed are: a liquid crystal composition which comprises a specific tetracyclic compound that enables the production of a nematic phase having a high upper-limit temperature and has high dielectric anisotropy as a first component and a specific compound having high positive dielectric anisotropy as a second component, and which has positive dielectric anisotropy; and a liquid crystal display element comprising the composition.

FIELD OF THE INVENTION

The invention relates mainly to a liquid crystal composition suitablefor use in an active matrix (AM) element and so forth, and an AM elementand so forth that contains the composition. More specifically, theinvention relates to a liquid crystal composition having positivedielectric anisotropy, and an element containing the composition andhaving a mode such as a twisted nematic (TN) mode, an opticallycompensated bend (OCB) mode, an in-plane switching (IPS) mode or apolymer sustained alignment (PSA) mode.

BACKGROUND OF THE INVENTION

In a liquid crystal display element, a classification based on anoperating mode for liquid crystals includes modes of phase change (PC),twisted nematic (TN), super twisted nematic (STN), electricallycontrolled birefringence (ECB), optically compensated bend (OCB),in-plane switching (IPS), vertical alignment (VA) and polymer sustainedalignment (PSA). A classification based on a driving mode in the elementincludes a passive matrix (PM) and an active matrix (AM). The PM isfurther classified into static, multiplex and so forth, and the AM isclassified into a thin film transistor (TFT), a metal-insulator-metal(MIM) and so forth. The TFT is further classified into amorphous siliconand polycrystal silicon. The latter is classified into a hightemperature type and a low temperature type according to the productionprocess. A classification based on a light source includes a reflectiontype utilizing natural light, a transmission type utilizing a backlightand a semi-transmission type utilizing both natural light and abacklight.

These elements contain a liquid crystal composition having suitablecharacteristics. The liquid crystal composition has a nematic phase.General characteristics of the composition should be improved to give anAM element having good general characteristics. Table 1 below summarizesthe relationship between the general characteristics of the two. Thegeneral characteristics of the composition will be explained furtherbased on a commercially available AM element. The temperature range of anematic phase relates to the temperature range in which the element canbe used. A desirable maximum temperature of the nematic phase is 70° C.or higher and a desirable minimum temperature of the nematic phase is−10° C. or lower. The viscosity of the composition relates to theresponse time of the element. A short response time is desirable fordisplaying moving images on the element. Accordingly, a small viscosityof the composition is desirable. A small viscosity at a low temperatureis more desirable.

TABLE 1 General Characteristics of Composition and AM Device GeneralCharacteristics General Characteristics No. of Composition of AM Device1 wide temperature range wide usable temperature of a nematic phaserange 2 small viscosity ¹⁾ short response time 3 suitable opticalanisotropy large contrast ratio 4 large positive or negative lowthreshold voltage and small dielectric anisotropy electric powerconsumption large contrast ratio 5 large specific resistance largevoltage holding ratio and large contrast ratio 6 high stability toultraviolet long service life light and heat ¹⁾ A liquid crystalcomposition can be injected into a liquid crystal cell in a shorterperiod of time.

The optical anisotropy of the composition relates to the contrast ratioof the element. The product (Δn×d) of the optical anisotropy (Δn) of thecomposition and the cell gap (d) of the element is designed so as tomaximize the contrast ratio. A suitable value of the product depends onthe kinds of operating mode. In an element having a TN mode, a suitablevalue is about 0.45 micrometer. In this case, a composition having alarge optical anisotropy is desirable for an element having a small cellgap. A large dielectric anisotropy of the composition contributes to alow threshold voltage, small electric power consumption and a largecontrast ratio of the element. Accordingly, a large dielectricanisotropy is desirable. A large specific resistance of the compositioncontributes to a large voltage holding ratio and a large contrast ratioof the element. Accordingly, a composition having a large specificresistance is desirable at room temperature and also at a hightemperature in the initial stage. A composition having a large specificresistance is desirable at room temperature and also at a hightemperature after it has been used for a long time. The stability of thecomposition to ultraviolet light and heat relates to the service life ofthe liquid crystal display element. In the case where the stability ishigh, the element has a long service life. These characteristics aredesirable for an AM element used in a liquid crystal projector, a liquidcrystal television and so forth.

A composition having positive dielectric anisotropy is used for an AMelement having a TN mode. On the other hand, a composition havingnegative dielectric anisotropy is used for an AM element having a VAmode. A composition having positive or negative dielectric anisotropy isused for an AM element having an IPS mode. A composition having positiveor negative dielectric anisotropy is used for an AM element having a PSAmode. Examples of liquid crystal compositions having positive dielectricanisotropy are disclosed in the following patent document.

PRIOR ART Patent Document

Patent document No. 1: JP Publication H10-251186 A (1998).

A desirable AM element has characteristics such as a wide temperaturerange in which the element can be used, a short response time, a largecontrast ratio, a low threshold voltage, a large voltage holding ratioand a long service life. Response time that is even one millisecondshorter than that of the other elements is desirable. Thus, acomposition having characteristics such as a high maximum temperature ofa nematic phase, a low minimum temperature of a nematic phase, a smallviscosity, a large optical anisotropy, a large dielectric anisotropy, alarge specific resistance, a high stability to ultraviolet light and ahigh stability to heat is desirable.

OUTLINE OF THE INVENTION Subject to be Solved by the Invention

One of the aims of the invention is to provide a liquid crystalcomposition that satisfies at least one of characteristics such as ahigh maximum temperature of a nematic phase, a low minimum temperatureof a nematic phase, a small viscosity, a large optical anisotropy, alarge dielectric anisotropy, a large specific resistance, a highstability to ultraviolet light and a high stability to heat. Another aimis to provide a liquid crystal composition that is suitably balancedregarding at least two of the characteristics. A further aim is toprovide a liquid crystal display element that contains such acomposition. An additional aim is to provide a liquid crystalcomposition that has a large optical anisotropy, a large dielectricanisotropy, a high stability to ultraviolet light and so forth, and isto provide an AM element that has a short response time, a large voltageholding ratio, a large contrast ratio, a long service life and so forth.

Means for solving the Subject

The invention concerns a liquid crystal composition that has a nematicphase and includes at least one compound selected from the group ofcompounds represented by formula (1) as a first component and at leastone compound selected from the group of compounds represented by formula(2) as a second component, and concerns a liquid crystal display elementcontaining this composition:

wherein R¹ and R² are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons or alkenyl having 2 to 12 carbons; the ring A andthe ring B are independently 1,4-cyclohexylene or 1,4-phenylene; thering C and the ring D are independently 1,4-cyclohexylene,1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene; X¹and X² are independently hydrogen or fluorine; and Y¹ is fluorine,chlorine or trifluoromethoxy.

Effect of the Invention

An advantage of the invention is a liquid crystal composition thatsatisfies at least one of characteristics such as a high maximumtemperature of a nematic phase, a low minimum temperature of a nematicphase, a small viscosity, a large optical anisotropy, a large dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat. One aspect of the invention is aliquid crystal composition that is suitably balanced regarding at leasttwo of the characteristics. Another aspect is a liquid crystal displayelement that contains such a composition. A further aspect is acomposition that has a large optical anisotropy, a large dielectricanisotropy, a high stability to ultraviolet light and so forth, and anAM element that has a short response time, a large voltage holdingratio, a large contrast ratio, a long service life and so forth.

Embodiment to Carry Out the Invention

Usage of the terms in the specification and claims is as follows. Theliquid crystal composition of the invention and the liquid crystaldisplay element of the invention may be abbreviated to “the composition”and “the element,” respectively. “A liquid crystal display element” is ageneric term for a liquid crystal display panel and a liquid crystaldisplay module. “A liquid crystal compound” is a generic term for acompound having a liquid crystal phase such as a nematic phase or asmectic phase, and also for a compound having no liquid crystal phasesbut being useful as a component of a composition. Such a useful compoundhas a six-membered ring such as 1,4-cyclohexylene and 1,4-phenylene, anda rod-like molecular structure. An optically active compound and apolymerizable compound may occasionally be added to the composition.Even in the case where these compounds are liquid crystalline, thecompounds are classified as an additive herein. At least one compoundselected from the group of compounds represented by formula (1) may beabbreviated to “the compound (1).” “The compound (1)” means onecompound, or two or more compounds represented by formula (1). The samerules apply to compounds represented by the other formulas. “Arbitrary”is used not only in cases where the position is arbitrary but also incases where the number is arbitrary. However, it is not used in caseswhere the number is 0 (zero).

A higher limit of the temperature range of a nematic phase may beabbreviated to “the maximum temperature.” A lower limit of thetemperature range of a nematic phase may be abbreviated to “the minimumtemperature.” That “specific resistance is large” means that acomposition has a large specific resistance at room temperature and alsoat a temperature close to the maximum temperature of a nematic phase inthe initial stage, and that the composition has a large specificresistance at room temperature and also at a temperature close to themaximum temperature of a nematic phase even after it has been used for along time. That “a voltage holding ratio is large” means that an elementhas a large voltage holding ratio at room temperature and also at atemperature close to the maximum temperature of a nematic phase in theinitial stage, and that the element has a large voltage holding ratio atroom temperature and also at a temperature close to the maximumtemperature of a nematic phase even after it has been used for a longtime. When characteristics such as optical anisotropy are explained,values which are obtained according to the measuring methods describedin Examples will be used. A first component means one compound, or twoor more compounds. “The ratio of the first component” is expressed as apercentage by weight (% by weight) of the first component based on thetotal weight of the liquid crystal composition. The same rule applies tothe ratio of a second component and so forth. The ratio of an additivemixed with the composition is expressed as a percentage by weight (% byweight) or weight parts per million (ppm) based on the total weight ofthe liquid crystal composition.

The symbol R¹ is used for a plurality of compounds in the chemicalformulas of component compounds. The meanings of R¹ may be the same ordifferent in two arbitrary compounds among these. In one case, forexample, R¹ of the compound (1-1) is ethyl and R¹ of the compound (1-2)is ethyl. In another case, R¹ of the compound (1-1) is ethyl and R¹ ofthe compound (1-2) is propyl. The same rule applies to the symbols R²,X¹ and so forth. In a chemical formula, “CL” stands for chlorine.

The invention includes the following items.

-   Item 1. A liquid crystal composition that has a nematic phase and    includes at least one compound selected from the group of compounds    represented by formula (1) as a first component and at least one    compound selected from the group of compounds represented by    formula (2) as a second component:

wherein R¹ and R² are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons or alkenyl having 2 to 12 carbons; the ring A andthe ring B are independently 1,4-cyclohexylene or 1,4-phenylene; thering C and the ring D are independently 1,4-cyclohexylene,1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene; X¹and X² are independently hydrogen or fluorine; and Y¹ is fluorine,chlorine or trifluoromethoxy.

-   Item 2. The liquid crystal composition according to item 1, wherein    the first component is at least one compound selected from the group    of compounds represented by formula (1-1) and formula (1-2):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; X¹ and X² are independentlyhydrogen or fluorine; and Y¹ is fluorine, chlorine or trifluoromethoxy.

-   Item 3. The liquid crystal composition according to item 2, wherein    the first component is at least one compound selected from the group    of compounds represented by formula (1-1).-   Item 4. The liquid crystal composition according to any one of items    1 to 3, wherein the second component is at least one compound    selected from the group of compounds represented by formula (2-1) to    formula (2-3):

wherein R² is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons; X¹ and X² are independentlyhydrogen or fluorine; and Y¹ is fluorine, chlorine or trifluoromethoxy.

-   Item 5. The liquid crystal composition according to item 4, wherein    the second component is at least one compound selected from the    group of compounds represented by formula (2-1).-   Item 6. The liquid crystal composition according to any one of items    1 to 5, wherein the ratio of the first component is in the range of    5% by weight to 50% by weight and the ratio of the second component    is in the range of 5% by weight to 50% by weight, based on the total    weight of the liquid crystal composition.-   Item 7. The liquid crystal composition according to any one of items    1 to 6, further including at least one compound selected from the    group of compounds represented by formula (3) as a third component:

wherein R³ and R⁴ are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons, alkenyl having 2 to 12, or alkenyl having 2 to12 carbons in which arbitrary hydrogen is replaced by fluorine; the ringE, the ring F and the ring G are independently 1,4-cyclohexylene,1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z¹ and Z² are independently a single bond,ethylene or carbonyloxy; and m is 0 or 1.

-   Item 8. The liquid crystal composition according to item 7, wherein    the third component is at least one compound selected from the group    of compounds represented by formula (3-1) to formula (3-6):

wherein R³ and R⁴ are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons, alkenyl having 2 to 12 carbons, or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine.

-   Item 9. The liquid crystal composition according to item 8, wherein    the third component is at least one compound selected from the group    of compounds represented by formula (3-1).-   Item 10. The liquid crystal composition according to item 8, wherein    the third component is a mixture of at least one compound selected    from the group of compounds represented by formula (3-1) and at    least one compound selected from the group of compounds represented    by formula (3-4).-   Item 11. The liquid crystal composition according to item 8, wherein    the third component is a mixture of at least one compound selected    from the group of compounds represented by formula (3-1) and at    least one compound selected from the group of compounds represented    by formula (3-6).-   Item 12. The liquid crystal composition according to item 8, wherein    the third component is a mixture of at least one compound selected    from the group of compounds represented by formula (3-1), at least    one compound selected from the group of compounds represented by    formula (3-4), and at least one compound selected from the group of    compounds represented by formula (3-6).-   Item 13. The liquid crystal composition according to any one of    items 7 to 12, wherein the ratio of the third component is in the    range of 40% by weight to 85% by weight based on the total weight of    the liquid crystal composition.-   Item 14. The liquid crystal composition according to any one of    items 1 to 13, further including at least one compound selected from    the group of compounds represented by formula (4) as a fourth    component:

wherein R⁵ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; the ring H is independently1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene or 2,5-pyrimidine; Z³is independently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹ and X² are independently hydrogen or fluorine;Y¹ is fluorine, chlorine or trifluoromethoxy; and o is 1 or 2.

-   Item 15. The liquid crystal composition according to item 14,    wherein the fourth component is at least one compound selected from    the group of compounds represented by formula (4-1) to formula    (4-12):

wherein R⁵ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons.

-   Item 16. The liquid crystal composition according to item 15,    wherein the fourth component is at least one compound selected from    the group of compounds represented by formula (4-9).-   Item 17. The liquid crystal composition according to item 15,    wherein the fourth component is at least one compound selected from    the group of compounds represented by formula (4-10).-   Item 18. The liquid crystal composition according to item 15,    wherein the fourth component is at least one compound selected from    the group of compounds represented by formula (4-11).-   Item 19. The liquid crystal composition according to item 15,    wherein the fourth component is a mixture of at least one compound    selected from the group of compounds represented by formula (4-6)    and at least one compound selected from the group of compounds    represented by formula (4-11).-   Item 20. The liquid crystal composition according to item 15,    wherein the fourth component is a mixture of at least one compound    selected from the group of compounds represented by formula (4-9)    and at least one compound selected from the group of compounds    represented by formula (4-11).-   Item 21. The liquid crystal composition according to any one of    items 14 to 20, wherein the ratio of the fourth component is in the    range of 5% by weight to 40% by weight based on the total weight of    the liquid crystal composition.-   Item 22. The liquid crystal composition according to any one of    items 1 to 21, wherein the maximum temperature of a nematic phase is    70° C. or higher, the optical anisotropy (25° C.) at a wavelength of    589 nanometers is 0.08 or more, and the dielectric anisotropy (25°    C.) at a frequency of 1 kHz is 2 or more.-   Item 23. A liquid crystal display element containing the liquid    crystal composition according to any one of items 1 to 22.-   Item 24. The liquid crystal display element according to item 23,    wherein an operating mode of the liquid crystal display element is a    TN mode, an OCB mode, an IPS mode or a PSA mode, and a driving mode    of the liquid crystal display element is an active matrix mode.

The invention further includes the following items: (1) the compositiondescribed above that further includes an optically active compound; (2)the composition described above that further includes an additive, suchas an antioxidant, an ultraviolet light absorber, an antifoaming agent,a polymerizable compound and/or a polymerization initiator. (3) an AMelement that contains the composition described above; (4) an elementthat has TN, ECB, OCB, IPS or PSA and contains the composition describedabove; (5) a transmission-type element that contains the compositiondescribed above; (6) use of the composition described above as acomposition having a nematic phase; and (7) use as an optically activecomposition prepared by the addition of an optically active compound tothe composition described above.

The composition of the invention will be explained in the followingorder. First, the constitution of component compounds in the compositionwill be explained. Second, main characteristics of the componentcompounds and main effects of these compounds on the composition will beexplained. Third, a combination of components in the composition,desirable ratios of the component compounds and the basis thereof willbe explained. Fourth, a desirable embodiment of the component compoundswill be explained. Fifth, specific examples of the component compoundswill be shown. Sixth, additives that may be mixed with the compositionwill be explained. Seventh, methods for synthesizing the componentcompounds will be explained. Last, use of the composition will beexplained.

First, the constitution of component compounds in the composition willbe explained. The compositions of the invention are classified into thecomposition A and the composition B. The composition A may furtherinclude any other liquid crystal compound, an additive and an impurity.“Any other liquid crystal compound” is a liquid crystal compound that isdifferent from the compound (1), the compound (2), the compound (3) andthe compound (4). Such a compound is mixed with the composition for thepurpose of further adjusting characteristics of the composition. Of anyother liquid crystal compound, a smaller amount of a cyano compound isdesirable in view of its stability to heat or ultraviolet light. A moredesirable ratio of the cyano compound is 0% by weight. The additiveincludes an optically active compound, an antioxidant, an ultravioletlight absorber, a coloring matter, an antifoaming agent, a polymerizablecompound and a polymerization initiator. The impurity is compounds andso forth which have contaminated component compounds in a process suchas their synthesis. Even in the case where the compound is liquidcrystalline, it is classified into the impurity herein.

The composition B consists essentially of compounds selected from thegroup of the compound (1), the compound (2), the compound (3) and thecompound (4). The term “essentially” means that the composition may alsoinclude an additive and an impurity, but does not include any liquidcrystal compound other than these compounds. The composition B has asmaller number of components than the composition A. The composition Bis preferable to the composition A in view of cost reduction. Thecomposition A is preferable to the composition B in view of the factthat physical properties can be further adjusted by adding any otherliquid crystal compound.

Second, main characteristics of the component compounds and main effectsof the compounds on the characteristics of the composition will beexplained. The main characteristics of the component compounds aresummarized in Table 2 on the basis of the effects of the invention. InTable 2, the symbol L stands for “large” or “high”, the symbol M standsfor “medium”, and the symbol S stands for “small” or “low.” The symbolsL, M and S are classified according to a qualitative comparison amongthe component compounds, and 0 (zero) means that “a value is nearlyzero.”

TABLE 2 Characteristics of Compounds Compounds Compound (1) Compound (2)Compound (3) Compound (4) Maximum Temperature L M S-L S-M Viscosity L LS-M M-L Optical Anisotropy L M-L S-L M-L Dielectric Anisotropy M-L L 0S-L Specific Resistance L L L L

Main effects of the component compounds on the characteristics of thecomposition upon mixing the component compounds with the composition areas follows. The compound (1) increases the maximum temperature, orincreases the dielectric anisotropy. The compound (2) increases thedielectric anisotropy. The compound (3) increases the maximumtemperature, or decreases the viscosity. The compound (4) decreases theminimum temperature, and increases the dielectric anisotropy.

Third, a combination of the components in the composition, desirableratios of the component compounds and the basis thereof will beexplained. A combination of the components in the composition is thefirst and second components, the first, second and third components, thefirst, second and fourth components, and the first, second, third andfourth components.

Desirable ratios of the component compounds and the basis thereof willbe explained. A desirable ratio of the first component is 5% by weightor more for increasing the maximum temperature and for increasing thedielectric anisotropy, and 50% by weight or less for decreasing theminimum temperature. A more desirable ratio is in the range of 5% byweight to 25% by weight. An especially desirable ratio is in the rangeof 5% by weight to 20% by weight.

A desirable ratio of the second component is 5% by weight or more forincreasing the dielectric anisotropy, and 50% by weight or less fordecreasing the minimum temperature. A more desirable ratio is in therange of 5% by weight to 25% by weight. An especially desirable ratio isin the range of 5% by weight to 20% by weight.

A desirable ratio of the third component is 40% by weight or more fordecreasing the viscosity, and 85% by weight or less for increasing thedielectric anisotropy. A more desirable ratio is in the range of 45% byweight to 80% by weight. An especially desirable ratio is in the rangeof 50% by weight to 75% by weight.

The fourth component is suitable for the preparation of a compositionhaving an especially large dielectric anisotropy. A desirable ratio ofthis component is in the range of 5% by weight to 40% by weight. Amoredesirable ratio is in the range of 5% by weight to 35% by weight. Anespecially desirable ratio is in the range of 5% by weight to 30% byweight.

Fourth, a desirable embodiment of the component compounds will beexplained. R¹ and R² are independently alkyl having 1 to 12 carbons,alkoxy having 1 to 12 carbons or alkenyl having 2 to 12 carbons.Desirable R¹ or R² is alkyl having 1 to 12 carbons for increasing thestability to ultraviolet light or heat, for instance. R³ and R⁴ areindependently alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine. DesirableR³ is alkenyl having 2 to 12 carbons for decreasing the minimumtemperature or for decreasing the viscosity. Desirable R⁴ is alkylhaving 1 to 12 carbons for increasing the stability to ultravioletlight, heat or the like. R⁵ is alkyl having 1 to 12 carbons or alkenylhaving 2 to 12 carbons. Desirable R⁵ is alkyl having 1 to 12 carbons forincreasing the stability to ultraviolet light, heat or the like.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptylor octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl or heptylfor decreasing the viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy or heptyloxy. More desirable alkoxy is methoxy or ethoxy fordecreasing the viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. More desirablealkenyl is vinyl, 1-propenyl, 3-butenyl or 3-pentenyl for decreasing theviscosity. A desirable configuration of —CH═CH— in the alkenyl dependson the position of the double bond. Trans is preferable in the alkenylsuch as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl and3-hexenyl for decreasing the viscosity, for instance. Cis is preferablein the alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl. In thealkenyl, straight-chain alkenyl is preferable to branched-chain alkenyl.

Desirable examples of alkenyl in which arbitrary hydrogen is replaced byfluorine are 2,2-difluorovinyl, 3,3-difluoro-2-propenyl,4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl and6,6-difluoro-5-hexenyl. More desirable examples are 2,2-difluorovinyland 4,4-difluoro-3-butenyl for decreasing the viscosity.

The ring A and the ring B are independently 1,4-cyclohexylene or1,4-phenylene. Desirable ring A is 1,4-cyclohexylene for decreasing theviscosity, and desirable ring B is 1,4-phenylene for increasing theoptical anisotropy. The ring C and the ring D are independently1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene or3,5-difluoro-1,4-phenylene. Desirable ring C is 3-fluoro-1,4-phenylenefor increasing the dielectric anisotropy and desirable ring D is1,4-phenylene for increasing the optical anisotropy. The ring E, thering F and the ring G are independently 1,4-cyclohexylene,1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene. Desirable ring E, ring F or ring G is1,4-cyclohexylene for decreasing the viscosity, and 1,4-phenylene forincreasing the optical anisotropy. The ring H is 1,4-cyclohexylene,1,3-dioxane-2,5-diyl, 1,4-phenylene, 3-fluoro-1,4-phenylene,2,5-difluoro-1,4-phenylene or 2,5-pyrimidine, and two of the ring H maybe the same of different when o is 2. Desirable ring H is 1,4-phenylenefor increasing the optical anisotropy.

Z¹ and Z² are independently a single bond, ethylene or carbonyloxy.Desirable Z¹ or Z² is a single bond for decreasing the viscosity. Z³ isa single bond, ethylene, carbonyloxy or difluoromethyleneoxy, and two ofZ³ maybe the same or different when o is 2. Desirable Z³ is a singlebond for decreasing the viscosity.

X¹ and X² are independently hydrogen or fluorine. Desirable X¹ or X² isfluorine for increasing the dielectric anisotropy.

Y¹ is fluorine, chlorine or trifluoromethoxy. Desirable Y¹ is fluorinefor decreasing the minimum temperature.

m is 0 or 1. Desirable m is 0 for decreasing the viscosity.

o is 1 or 2. Desirable o is 2 for decreasing the minimum temperature.

Fifth, specific examples of the component compounds will be shown. Inthe desirable compounds described below, R⁶ is straight-chain alkylhaving 1 to 12 carbons. R⁷ is straight-chain alkyl having 1 to 12carbons or straight-chain alkoxy having 1 to 12 carbons. R⁸ and R⁹ areindependently straight-chain alkyl having 1 to 12 carbons orstraight-chain alkenly having 2 to 12 carbons. With regard to theconfiguration of 1,4-cyclohexylene in these compounds, trans ispreferable to cis for increasing the maximum temperature.

Desirable compound (1) are the compound (1-1-1) to the compound (1-1-3)and the compound (1-2-1) to the compound (1-2-3). More desirablecompound (1) are the compound (1-1-1), the compound (1-1-2), thecompound (1-2-1) and the compound (1-2-2). Especially desirable compound(1) is the compound (1-1-1). Desirable compound (2) are the compound(2-1-1), the compound (2-1-2), the compound (2-2-1), the compound(2-2-2), the compound (2-3-1) and the compound (2-3-2). More desirablecompound (2) are the compound (2-1-1), the compound (2-2-1) and thecompound (2-3-1). Especially desirable compound (2) is the compound(2-1-1). Desirable compound (3) are the compound (3-1-1) to the compound(3-6-1). More desirable compound (3) are the compound (3-1-1), thecompound (3-3-1), the compound (3-4-1) and the compound (3-6-1).Especially desirable compound (3) are the compound (3-1-1), the compound(3-4-1) and the compound (3-6-1). Desirable compound (4) are thecompound (4-1-1) to the compound (4-12-1) and the compound (4-13) to thecompound (4-18). More desirable compound (4) are the compound (4-9-1)and the compound (4-11-1). Especially desirable compound (4) is thecompound (4-11-1).

Sixth, additives which may be mixed with the composition will beexplained. Such additives include an optically active compound, anantioxidant, an ultraviolet light absorber, a coloring matter, anantifoaming agent, a polymerizable compound and a polymerizationinitiator. The optically active compound is mixed with the compositionfor the purpose of inducing a helical structure and giving a twist anglein liquid crystals. Examples of such compounds include the compound(5-1) to the compound (5-4). A desirable ratio of the optically activecompound is 5% by weight or less, and a more desirable ratio is in therange of 0.01% by weight to 2% by weight.

An antioxidant is mixed with the composition in order to prevent adecrease in specific resistance that is caused by heating under air, orto maintain a large voltage holding ratio at room temperature and alsoat a temperature close to the maximum temperature of a nematic phaseafter the element has been used for a long time.

Desirable examples of the antioxidant include the compound (6) where nis an integer from 1 to 9. In the compound (6), desirable n is 1, 3, 5,7 or 9. More desirable n is 1 or 7. The compound (6) where n is 1 iseffective in preventing a decrease in specific resistance that is causedby heating under air, because it has a large volatility. The compound(6) where n is 7 is effective in maintaining a large voltage holdingratio at room temperature and also at a temperature close to the maximumtemperature of a nematic phase even after the element has been used fora long time, because it has a small volatility. A desirable ratio of theantioxidant is 50 ppm or more for achieving its effect and is 600 ppm orless for avoiding a decrease in the maximum temperature or avoiding anincrease in the minimum temperature. A more desirable ratio is in therange of 100 ppm to 300 ppm.

Desirable examples of the ultraviolet light absorber include abenzophenone derivative, a benzoate derivative and a triazolederivative. A light stabilizer such as an amine having steric hindranceis also desirable. A desirable ratio of the ultraviolet light absorberor the light stabilizer is 50 ppm or more for achieving its effect andis 10,000 ppm or less for avoiding a decrease in the maximum temperatureor avoiding an increase in the minimum temperature. A more desirableratio is in the range of 100 ppm to 10,000 ppm.

A dichroic dye such as an azo dye or an anthraquinone dye is mixed withthe composition for adjusting to an element having a guest host (GH)mode. A desirable ratio of the coloring matter is in the range of 0.01%by weight to 10% by weight. An antifoaming agent such as dimethylsilicone oil or methyl phenyl silicone oil is mixed with the compositionfor preventing foam formation. A desirable ratio of the antifoamingagent is 1 ppm or more for achieving its effect and is 1,000 ppm or lessfor avoiding a poor display. A more desirable ratio is in the range of 1ppm to 500 ppm.

A polymerizable compound is mixed with the composition for adjusting toan element having a polymer sustained alignment (PSA) mode. Desirableexamples of the polymerizable compound include compounds having apolymerizable group, such as acrylates, methacrylates, vinyl compounds,vinyloxy compounds, propenyl ethers, epoxy compounds (oxythanes,oxetanes) and vinyl ketones. Especially desirable examples of thepolymerizable compound are acrylate derivatives or methacrylatederivatives. A desirable ratio of the polymerizable compound is 0.05% byweight or more for achieving its effect and is 10% by weight or less foravoiding a poor display. A more desirable ratio is in the range of 0.1%by weight to 2% by weight. The polymerizable compound is polymerized onirradiation with ultraviolet light or the like, preferably in thepresence of a suitable initiator such as a photopolymerizationinitiator. Suitable conditions for polymerization, suitable types of theinitiator and suitable amounts thereof are known to a person skilled inthe art and are described in the literature. For example, Irgacure 651(registered trademark), Irgacure 184 (registered trademark) or Darocure1173 (registered trademark) (Ciba Japan K.K.), each of which is aphotoinitiator, is suitable for radical polymerization. Thepolymerizable compound includes the photopolymerization initiatorpreferably in the range of 0.1% by weight to 5% by weight and mostpreferably in the range of 1% by weight to 3% by weight.

Seventh, methods for synthesizing the component compounds will beexplained. These compounds can be synthesized by known methods. Thesynthetic methods will be exemplified as follows. The compound (1-1-1)and the compound (2-1-1) are prepared by the method described in JPpublication H10-251186A (1998). The compound (3-1-1) and the compound(3-4-1) are prepared by the method described in JP publicationS59-176221 A (1984). The compound (4-5-1) and the compound (4-8-1) areprepared by the method described in JP publication H02-233626 A (1990).An antioxidant is commercially available. The compound with formula (6)where n is 1 is available from Sigma-Aldrich Corporation. The compound(6) where n is 7 and so forth is synthesized according to the methoddescribed in U.S. Pat. No. 3,660,505.

Compounds whose synthetic methods are not described above can beprepared according to the methods described in books such as OrganicSyntheses (John Wiley & Sons, Inc.), Organic Reactions (John Wiley &Sons, Inc.), Comprehensive Organic Synthesis (Pergamon Press), Newexperimental Chemistry Course (Shin Jikken Kagaku Kouza, in Japanese;Maruzen Co., Ltd.). The composition is prepared according to knownmethods using the compounds thus obtained. For example, the componentcompounds are mixed and dissolved in each other by heating.

Last, use of the composition will be explained. Most of the compositionhas a minimum temperature of −10° C. or lower, a maximum temperature of70° C. or higher, and an optical anisotropy in the range of 0.07 to0.20. An element containing the composition has a large voltage holdingratio. The composition is suitable for an AM element. The composition issuitable especially for an AM element having a transmission type. Thecomposition having an optical anisotropy in the range of 0.08 to 0.25,and the composition having an optical anisotropy also in the range of0.10 to 0.30 may be prepared by adjusting ratios of the componentcompounds or by mixing with any other liquid crystal compound. Thecomposition can be used as a composition having a nematic phase and asan optically active composition by adding an optically active compound.

The composition can be used for an AM element. It can also be used for aPM element. The composition can also be used for the AM element and thePM element having a mode such as PC, TN, STN, ECB, OCB, IPS, VA or PSA.It is especially desirable to use the composition for the AM elementhaving the TN, OCB or IPS mode. These elements may be of a reflectiontype, a transmission type or a semi-transmission type. It is desirableto use the composition for an element having the transmission type. Itcan be used for an amorphous silicon-TFT element or a polycrystalsilicon-TFT element. The composition is also usable for a nematiccurvilinear aligned phase (NCAP) element prepared by microcapsulatingthe composition, and for a polymer dispersed (PD) element in which athree-dimensional network-polymer is formed in the composition.

EXAMPLES

When a sample was a composition, it was measured as it was, and thevalue obtained was described here. When a sample was a compound, asample for measurement was prepared by mixing 15% by weight of thecompound and 85% by weight of mother liquid crystals. The characteristicvalues of the compound were calculated from values obtained bymeasurement, according to a method of extrapolation. That is:(extrapolated value)=[(measured value of a sample)−0.85×(measured valueof mother liquid crystals)]/0.15. When a smectic phase (or crystals)separated out in this ratio at 25° C., the ratio of the compound to themother liquid crystals was changed step by step in the order of (10% byweight/90% by weight), (5% by weight/95% by weight) and (1% byweight/99% by weight). The values of the maximum temperature, theoptical anisotropy, the viscosity and the dielectric anisotropy withregard to the compound were obtained by this extrapolation method.

The components of the mother liquid crystals were as follows. The ratioswere expressed as a percentage by weight.

Characteristics were measured according to the following methods. Mostmethods are described in the Standards of Electronic IndustriesAssociation of Japan, EIAJ•ED-2521 A or those with some modifications.

Maximum Temperature of a Nematic Phase (NI; ° C.): A sample was placedon a hot plate in a melting point apparatus equipped with a polarizingmicroscope and was heated at the rate of 1° C. per minute. Thetemperature was measured when part of the sample began to change from anematic phase to an isotropic liquid. A higher limit of the temperaturerange of a nematic phase may be abbreviated to “the maximumtemperature.”

Minimum Temperature of a Nematic Phase (Tc; ° C.): A sample having anematic phase was put in glass vials and then kept in freezers attemperatures of 0° C., −10° C., −20° C., −30° C. and −40° C. for 10days, and then the liquid crystal phases were observed. For example,when the sample maintained the nematic phase at −20° C. and changed tocrystals or a smectic phase at −30° C., Tc was expressed as ≦−20° C. Alower limit of the temperature range of a nematic phase may beabbreviated to “the minimum temperature.”

Viscosity (bulk viscosity; η; measured at 20° C.; mPa·s): Viscosity wasmeasured by use of an E-type viscometer.

Viscosity (rotational viscosity; γ1; measured at 25° C.; mPa·s):Measurement was carried out according to the method described in M.Imai, et al., Molecular Crystals and Liquid Crystals, Vol. 259, 37(1995). A sample was poured into an element in which the twist angle was0 degrees and the distance between the two glass substrates (cell gap)was 5 micrometers. A voltage with an increment of 0.5 volt in the rangeof 16 to 19.5 volts was applied stepwise to the TN element. After aperiod of 0.2 second with no voltage, a voltage was applied repeatedlyunder the conditions of only one rectangular wave (rectangular pulse;0.2 second) and of no voltage (2 seconds). The peak current and the peaktime of the transient current generated by the applied voltage weremeasured. The value of rotational viscosity was obtained from themeasured values and the calculating equation (8) on page 40 of the paperpresented by M. Imai, et al. The value of dielectric anisotropynecessary for this calculation was obtained by use of the element thathad been used for the measurement of this rotational viscosity,according to the method that will be described below.

Optical Anisotropy (refractive index anisotropy; Δn; measured at 25°C.): Measurement was carried out by use of an Abbe refractometer with apolarizing plate mounted on the ocular, using light at a wavelength of589 nanometers. The surface of the main prism was rubbed in onedirection, and then a sample was dropped on the main prism. A refractiveindex (n∥) was measured when the direction of polarized light wasparallel to that of the rubbing. A refractive index (n⊥) was measuredwhen the direction of polarized light was perpendicular to that of therubbing. The value of optical anisotropy was calculated from theequation: Δn=n∥−n⊥.

Dielectric Anisotropy (Δε; measured at 25° C.): A sample was poured intoa TN element in which the distance between the two glass substrates(cell gap) was 9 micrometers and the twist angle was 80 degrees. Sinewaves (10 V, 1 kHz) were applied to this element, and a dielectricconstant (ε∥) in the major axis direction of liquid crystal moleculeswas measured after 2 seconds. Sine waves (0.5 V, 1 kHz) were applied tothe element and a dielectric constant (ε⊥) in the minor axis directionof the liquid crystal molecules was measured after 2 seconds. The valueof dielectric anisotropy was calculated from the equation:

Δε=ε∥−ε⊥.

Threshold Voltage (Vth; measured at 25° C.; V): Measurement was carriedout with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. A sample waspoured into a TN element having a normally white mode, in which thedistance between the two glass substrates (cell gap) was about 4.45/Δn(micrometers) and the twist angle was 80 degrees. Voltage to be appliedto the element (32 Hz, rectangular waves) was stepwise increased in 0.02V increments from 0 V up to 10 V. During the increase, the element wasirradiated with light in the perpendicular direction, and the amount oflight passing through the element was measured. A voltage-transmittancecurve was prepared, in which the maximum amount of light corresponded to100% transmittance and the minimum amount of light corresponded to 0%transmittance. The threshold voltage was voltage at 90% transmittance.

Voltage Holding Ratio (VHR-1; measured at 25° C.; %): A TN element usedfor measurement had a polyimide-alignment film, and the distance betweenthe two glass substrates (cell gap) was 5 micrometers. A sample waspoured into the element, and then the element was sealed with aUV-polymerizable adhesive. A pulse voltage (60 microseconds at 5 V) wasapplied to the TN element and the element was charged. A decreasingvoltage was measured for 16.7 milliseconds with a high-speed voltmeter,and the area A between the voltage curve and the horizontal axis in aunit cycle was obtained. The area B was an area without the decrease.The voltage holding ratio was the percentage of the area A to the areaB.

Voltage Holding Ratio (VHR-2; measured at 80° C.; %): A TN element usedfor measurement had a polyimide-alignment film, and the distance betweenthe two glass substrates (cell gap) was 5 micrometers. A sample waspoured into the element, and then the element was sealed with aUV-polymerizable adhesive. A pulse voltage (60 microseconds at 5 V) wasapplied to the TN element and the element was charged. A decreasingvoltage was measured for 16.7 milliseconds with a high-speed voltmeterand the area A between the voltage curve and the horizontal axis in aunit cycle was obtained. The area B was an area without the decrease.The voltage holding ratio was a percentage of the area A to the area B.

Voltage Holding Ratio (VHR-3; measured at 25° C.; %): The stability toultraviolet light was evaluated by measuring a voltage holding ratioafter irradiation with ultraviolet light. A composition having a largeVHR-3 has a high stability to ultraviolet light. A TN element used formeasurement had a polyimide-alignment film and the cell gap was 5micrometers. A sample was poured into this element, and then the elementwas irradiated with light for 20 minutes. The light source was an ultrahigh-pressure mercury lamp USH-500D (produced by Ushio, Inc.), and thedistance between the element and the light source was 20 centimeters. Inthe measurement of VHR-3, a decreasing voltage was measured for 16.7milliseconds. The value of VHR-3 is preferably 90% or more, and morepreferably 95% or more.

Voltage Holding Ratio (VHR-4; measured at 25° C.; %): A TN element intowhich a sample was poured was heated in a constant-temperature bath at80° C. for 500 hours, and then the stability to heat was evaluated bymeasuring the voltage holding ratio. A composition having a large VHR-4has a high stability to heat. In the measurement of VHR-4, a decreasingvoltage was measured for 16.7 milliseconds.

Response Time (τ; measured at 25° C.; millisecond): Measurement wascarried out with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. The low-passfilter was set at 5 kHz. A sample was poured into a TN element having anormally white mode, in which the cell gap between the two glasssubstrates was 5.0 micrometers and the twist angle was 80 degrees.Rectangular waves (60 Hz, 5 V, 0.5 second) were applied to this element.The element was simultaneously irradiated with light in theperpendicular direction, and the amount of light passing through theelement was measured. The maximum amount of light corresponded to 100%transmittance, and the minimum amount of light corresponded to 0%transmittance. Rise time (τr; millisecond) was the time required for achange from 90% to 10% transmittance. Fall time (τf; millisecond) wasthe time required for a change from 10% to 90% transmittance. Theresponse time was the sum of the rise time and the fall time thusobtained.

Specific Resistance (ρ; measured at 25° C.; Ω cm): A sample of 1.0milliliter was poured into a vessel equipped with electrodes. DC voltage(10 V) was applied to the vessel, and the DC current was measured after10 seconds. The specific resistance was calculated from the followingequation.

(specific resistance)=[(voltage)×(electric capacity of vessel)]/[(DCcurrent)×(dielectric constant in vacuum)].

Gas Chromatographic Analysis: A gas chromatograph Model GC-14B made byShimadzu Corporation was used for measurement. The carrier gas washelium (2 milliliters per minute). The sample injector and the detector(FID) were set to 280° C. and 300° C., respectively. A capillary columnDB-1 (length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer, dimethylpolysiloxane as the stationary phase, non-polar)made by Agilent Technologies, Inc. was used for the separation ofcomponent compounds. After the column had been kept at 200° C. for 2minutes, it was further heated to 280° C. at the rate of 5° C. perminute. A sample was dissolved in acetone (0.1% by weight), and 1microliter of the solution was injected into the sample injector. Arecorder used was a Model C-R5A Chromatopac Integrator made by ShimadzuCorporation or its equivalent. The resulting gas chromatogram showed theretention time of peaks and the peak areas corresponding to thecomponent compounds.

Solvents for diluting the sample may also be chloroform, hexane and soforth. The following capillary columns may also be used in order toseparate the component compounds: HP-1 (length 30 meters, bore 0.32millimeter, film thickness 0.25 micrometer) made by Agilent TechnologiesInc., Rtx-1 (length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer) made by Restek Corporation, and BP-1 (length 30 meters, bore0.32 millimeter, film thickness 0.25 micrometer) made by SGEInternational Pty. Ltd. A capillary column CBP1-M50-025 (length 50meters, bore 0.25 millimeter, film thickness 0.25 micrometer) made byShimadzu Corporation may also be used for the purpose of avoiding anoverlap of peaks of the compounds.

The ratio of the liquid crystal compounds included in the compositionmay be calculated according to the following method. The liquid crystalcompounds are detected by use of a gas chromatograph. The ratio of peakareas in the gas chromatogram corresponds to the ratio (molar ratio) ofthe liquid crystal compounds. When the capillary columns described aboveare used, the correction coefficient of respective liquid crystalcompounds may be regarded as 1 (one). Accordingly, the ratio (percentageby weight) of the liquid crystal compound can be calculated from theratio of peak areas.

The invention will be explained in detail by way of Examples. Theinvention is not limited by Examples described below. The compoundsdescribed in Comparative Examples and Examples were expressed as symbolsaccording to the definition in the following Table 3. In Table 3, theconfiguration of 1,4-cyclohexylene is trans. A parenthesized number nextto the symbolized compound in Example corresponds to the number of acompound. The symbol (−) means any other liquid crystal compound. Ratios(percentage) of liquid crystal compounds mean the percentages by weight(% by weight) based on the total weight of the liquid crystalcomposition. The liquid crystal composition further includes animpurity. Last, the characteristic values of the composition aresummarized.

TABLE 3 Method of Description of Compounds using Symbols R—(A₁)—Z₁—. ..—Z_(n)—(A_(n))—R′ Symbol 1) Left-terminal Group R— C_(n)H_(2n+1)— n—C_(n)H_(2n+1)O— nO— C_(m)H_(2m+1)OC_(n)H_(2n)— mOn— CH₂═CH— V—C_(n)H_(2n+1)—CH═CH— nV— CH₂═CH—C_(n)H_(2n)— Vn—C_(m)H_(2m+1)—CH═CH—C_(n)H_(2n)— mVn— CF₂═CH— VFF— CF₂═CH—C_(n)H_(2n)—VFFn— 2) Right-terminal Group —R′ —C_(n)H_(2n+1) —n —OC_(n)H_(2n+1) —On—CH═CH₂ —V —CH═CH—C_(n)H_(2n+1) —Vn —C_(n)H_(2n)—CH═CH₂ —nV —CH═CF₂ —VFF—F —F —Cl —CL —OCF₃ —OCF3 —C≡N —C 3) Bonding Group —Z_(n)— —C₂H₄— 2—COO— E —CH═CH— V —C≡C— T —CF₂O— X 4) Ring Structure —A_(n)—

H

B

B(F)

B(2F)

B(F,F)

B(2F,5F)

Py

G 5) Examples of Description Example 1. V2-BB(F)B-1

Example 2. 3-HB-CL

Example 3. 5-PyBB-F

Example 4. 3-BB(F,F)XB(F)-OCF3

Comparative Example 1

Example 42 was selected from the compositions disclosed in JPpublication H10-251186 A (1998). The basis of the selection was that thecomposition included the compound (1-1-1) and had the smallestrotational viscosity. This composition was prepared, and measuredaccording to the method described above, since there had been nodescriptions with regard to the rotational viscosity. The components andcharacteristics of the composition were as follows:

3-HB(F)XB(F,F)-F (—) 5% 3-HBBXB(F,F)-CF3 (—) 2% 3-HBBXB(F,F)-F (1-1-1)2% 5-HB-CL (4-1-1) 12% 3-HH-4 (3-1-1) 7% 3-HB-O2 (3-2-1) 20%3-H2HB(F,F)-F (4) 4% 3-HHB(F,F)-F (4-5-1) 8% 3-HBB(F,F)-F (4-8-1) 6%2-HHB(F)-F (4) 5% 3-HHB(F)-F (4) 5% 2-H2HB(F)-F (4) 2% 3-H2HB(F)-F (4)1% 5-H2HB(F)-F (4) 2% 3-HHBB(F,F)-F (—) 4% 3-HBXB-OCF3 (4) 4%5-HBXB(F,F)-CF3 (—) 4% 3-HHB-1 (3-4-1) 3% 3-HHB-01 (3-4-1) 4% NI = 70.6°C.; Δn = 0.088; Δε = 5.1; Vth = 2.07 V; γ1 = 120 mPa · s.

Comparative Example 2

Example 43 was selected from the compositions disclosed in JPpublication H10-251186 A (1998). The basis of the selection was that thecomposition included the compound (1-2-1), the compound (3-1-1) and thecompound (3-4-1) and had the smallest rotational viscosity. Thiscomposition was prepared, and measured according to the method describedabove, since there had been no descriptions with regard to therotational viscosity at 25° C. The components and characteristics of thecomposition were as follows:

3-HB(F,F)XB(F,F)-F (—) 4% 3-HHBXB(F,F)-F (1-2-1) 4% 3-BEB(F)-C (—) 8%3-HB-C (—) 8% V-HB-C (—) 8% 1V-HB-C (—) 8% 3-HB-O2 (3-2-1) 3% 3-HH-2V(3-1-1) 14% 3-HH-2V1 (3-1-1) 7% V2-HHB-1 (3-4-1) 7% 3-HHB-1 (3-4-1) 5%3-HHEB-F (—) 7% 3-H2BTB-2 (—) 6% 3-H2BTB-3 (—) 6% 3-H2BTB-4 (—) 5% NI =92.9° C.; Δn = 0.131; Δε = 9.5; Vth = 1.98 V; γ1 = 115 mPa · s.

Example 1

4-HBBXB(F,F)-F (1-1-1) 6% 5-HBBXB(F,F)-F (1-1-1) 5%4-BB(F)B(F,F)XB(F,F)-F (2-1-1) 7% 5-BB(F)B(F,F)XB(F,F)-F (2-1-1) 7%V-HH-3 (3-1-1) 44% 1V-HH-3 (3-1-1) 7% V-HHB-1 (3-4-1) 10% V2-HHB-1(3-4-1) 6% 3-BB(F,F)XB(F,F)-F (4-11-1) 8% NI = 86.2° C.; Tc ≦ −20° C.;Δn = 0.099; Δε = 5.5; Vth = 2.53 V; γ1 = 50.5 mPa · s; τ = 7.5 ms; VHR-1= 99.1%; VHR-2 = 98.2%; VHR-3 = 98.1%.

Example 2

3-HBBXB(F)-F (1-1-3) 4% 4-HBBXB(F)-F (1-1-3) 5% 3-HBB(F,F)XB(F,F)-F(2-3-1) 5% 4-HBB(F,F)XB(F,F)-F (2-3-1) 5% V-HH-3 (3-1-1) 39% V-HH-5(3-1-1) 8% 1V-HH-3 (3-1-1) 8% 2-HHB-1 (3-4-1) 4% 3-HHB-1 (3-4-1) 4%V2-BB(F)B-1 (3-6-1) 4% 3-HHB(F,F)-F (4-5-1) 6% 3-BB(F)B(F,F)-F (4-9-1)8% NI = 90.3° C.; Tc ≦ −20° C.; Δn = 0.099; Δε = 2.3; Vth = 3.75 V; γ1 =50.0 mPa · s; τ = 6.5 ms; VHR-1 = 99.0%; VHR-2 = 98.1%; VHR-3 = 98.0%.

Example 3

3-HBBXB(F)-OCF3 (1-1-2) 6% 4-HBBXB(F)-OCF3 (1-1-2) 6%3-HB(F)B(F,F)XB(F,F)-F (2-2-1) 3% 4-HB(F)B(F,F)XB(F,F)-F (2-2-1) 3%2-HH-3 (3-1-1) 25% 3-HH-4 (3-1-1) 14% V2-BB-1 (3-3-1) 4% 1V2-BB-1(3-3-1) 4% 3-HBB-2 (3-5-1) 5% 1V-HBB-2 (3-5-1) 5% V2-BB(F)B-1 (3-6-1) 3%V2-BB(F)B-2 (3-6-1) 3% 3-HGB(F,F)-F (4-17) 5% 5-HGB(F,F)-F (4-17) 5%3-GHB(F,F)-F (4-18) 4% 5-GHB(F,F)-F (4-18) 5% NI = 80.2° C.; Tc ≦ −20°C.; Δn = 0.102; Δε = 5.3; Vth = 2.67 V; γ1 = 68.2 mPa · s; τ = 8.7 ms;VHR-1 = 99.3%; VHR-2 = 98.3%; VHR-3 = 98.2%.

Example 4

3-HHBXB(F,F)-F (1-2-1) 9% 5-HHBXB(F,F)-F (1-2-1) 9%3-BB(F)B(F,F)XB(F)-OCF3 (2-1-2) 3% 5-BB(F)B(F,F)XB(F)-OCF3 (2-1-2) 3%V-HH-3 (3-1-1) 20% 1V-HH-3 (3-1-1) 8% 3-HH-O1 (3-1-1) 5% 7-HB-1 (3-2-1)5% 3-HB-O2 (3-2-1) 6% 2-BB(F)B-3 (3-6-1) 3% 2-BB(F)B-5 (3-6-1) 3%3-HB-CL (4-1-1) 5% 3-HHB(F,F)-F (4-5-1) 8% 3-HHXB(F,F)-F (4-6-1) 8%3-HBB-F (4-7-1) 5% NI = 82.9° C.; Tc ≦ −20° C.; Δn = 0.103; Δε = 4.0;Vth = 3.25 V; γ1 = 71.4 mPa · s; τ = 7.5 ms; VHR-1 = 99.2%; VHR-2 =98.3%; VHR-3 = 98.2%.

Example 5

3-HHBXB(F)-OCF3 (1-2-2) 4% 4-HHBXB(F)-OCF3 (1-2-2) 4%3-HB(F)B(F,F)XB(F)-OCF3 (2-2-2) 4% 4-HB(F)B(F,F)XB(F)-OCF3 (2-2-2) 3%3-HH-VFF (3-1) 5% V-HH-3 (3-1-1) 26% 1V-HH-3 (3-1-1) 8% V-HHB-1 (3-4-1)9% V2-HHB-1 (3-4-1) 9% 3-HB-CL (4-1-1) 10% 3-PyBB-F (4-10-1) 4% 5-PyBB-F(4-10-1) 4% 3-BB(F,F)XB(F,F)-F (4-11-1) 10% NI = 82.0° C.; Tc ≦ −20° C.;Δn = 0.106; Δε = 5.1; Vth = 2.56 V; γ1 = 49.2 mPa · s; τ = 7.9 ms; VHR-1= 99.1%; VHR-2 = 98.1%; VHR-3 = 98.0%.

Example 6

3-HHBXB(F)-F (1-2-3) 8% 4-HHBXB(F)-F (1-2-3) 8% 3-HBB(F,F)XB(F)-OCF3(2-3-2) 4% 4-HBB(F,F)XB(F)-OCF3 (2-3-2) 4% V-HH-3 (3-1-1) 47% V-HHB-1(3-4-1) 4% 3-HHB-O1 (3-4-1) 4% V2-BB(F)B-1 (3-6-1) 4% V2-BB(F)B-2(3-6-1) 3% 1V2-BB-F (4-2-1) 4% 3-BB(F,F)XB(F)-OCF3 (4-12-1) 6%3-HHXB(F)-OCF3 (4-13) 4% NI = 87.4° C.; Tc ≦ −20° C.; Δn = 0.108; Δε =3.8; Vth = 3.32 V; γ1 = 47.2 mPa · s; τ = 6.8 ms; VHR-1 = 99.3%; VHR-2 =98.2%; VHR-3 = 98.1%.

Example 7

3-HBBXB(F,F)-F (1-1-1) 3% 4-HBBXB(F,F)-F (1-1-1) 4%3-BB(F)B(F,F)XB(F,F)-F (2-1-1) 5% 4-BB(F)B(F,F)XB(F,F)-F (2-1-1) 5%3-HB(F)B(F,F)XB(F,F)-F (2-2-1) 5% V-HH-3 (3-1-1) 39% 1V-HH-3 (3-1-1) 11%V-HHB-1 (3-4-1) 4% 1V2-BB-CL (4-3-1) 3% 3-HHB-CL (4-4-1) 6% 3-HBB-F(4-7-1) 4% 3-HBB(F,F)-F (4-8-1) 3% 3-BB(F,F)XB(F)-F (4-14) 8% NI = 81.0°C.; Tc ≦ −20° C.; Δn = 0.104; Δε = 5.1; Vth = 2.65 V; γ1 = 50.6 mPa · s;τ = 8.0 ms; VHR-1 = 99.0%; VHR-2 = 98.1%; VHR-3 = 98.0%.

Example 8

3-HBBXB(F)-F (1-1-1) 4% 4-HBBXB(F)-F (1-1-1) 5% 3-HB(F)B(F,F)XB(F,F)-F(2-2-1) 8% 3-HHEH-5 (3) 3% 4-HHEH-5 (3) 3% 2-HH-3 (3-1-1) 25% 3-HH-4(3-1-1) 23% V2-BB-1 (3-3-1) 4% 2-BB(F)B-3 (3-6-1) 9% 2-BB(F)B-5 (3-6-1)8% 3-HHEB(F,F)-F (4-15) 4% 3-HBEB(F,F)-F (4-16) 4% NI = 84.3° C.; Tc ≦−20° C.; Δn = 0.101; Δε = 3.1; Vth = 3.60 V; γ1 = 52.4 mPa · s; τ = 7.1ms; VHR-1 = 99.0%; VHR-2 = 98.0%; VHR-3 = 98.0%.

Example 9

3-HHBXB(F,F)-F (1-2-1) 4% 4-HHBXB(F,F)-F (1-2-1) 4% 3-HBB(F,F)XB(F,F)-F(2-3-1) 3% 4-HBB(F,F)XB(F,F)-F (2-3-1) 3% V-HH-3 (3-1-1) 42% V-HHB-1(3-4-1) 7% V2-HHB-1 (3-4-1) 8% 1-BB(F)B-2V (3-6-1) 3% 3-HHB(F,F)-F(4-5-1) 6% 3-BB(F,F)XB(F,F)-F (4-11-1) 6% 3-BB(F,F)XB(F)-OCF3 (4-12-1)6% 2-HHBB(F,F)-F (—) 4% 3-HHBB(F,F)-F (—) 4% NI = 90.2° C.; Tc ≦ −20°C.; Δn = 0.099; Δε = 4.4; Vth = 3.18 V; γ1 = 73.1 mPa · s; τ = 7.6 ms;VHR-1 = 99.1%; VHR-2 = 98.2%; VHR-3 = 98.1%.

The compositions of Examples 1 to 9 have a small rotational viscosity incomparison with those in Comparative Examples 1 and 2. Thus, the liquidcrystal composition of the invention is so much superior incharacteristics to the compositions disclosed in the patent document No.1.

INDUSTRIAL APPLICABILITY

The invention provides a liquid crystal composition that satisfies atleast one of characteristics such as a high maximum temperature of anematic phase, a low minimum temperature of a nematic phase, a smallviscosity, a large optical anisotropy, a large positive dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat, or that is suitably balancedregarding at least two of the characteristics. A liquid crystal displayelement containing such a liquid crystal composition becomes an AMelement that has a short response time, a large voltage holding ratio, alarge contrast ratio, a long service life and so forth, and thus it canbe used for a liquid crystal projector, a liquid crystal television andso forth.

1. A liquid crystal composition that has a nematic phase and includes atleast one compound selected from the group of compounds represented byformula (1) as a first component and at least one compound selected fromthe group of compounds represented by formula (2) as a second component:

wherein R¹ and R² are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons or alkenyl having 2 to 12 carbons; the ring A andthe ring B are independently 1,4-cyclohexylene or 1,4-phenylene; thering C and the ring D are independently 1,4-cyclohexylene,1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene; X¹and X² are independently hydrogen or fluorine; and Y¹ is fluorine,chlorine or trifluoromethoxy.
 2. The liquid crystal compositionaccording to claim 1, wherein the first component is at least onecompound selected from the group of compounds represented by formula(1-1) and formula (1-2):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; X¹ and X² are independentlyhydrogen or fluorine; and Y¹ is fluorine, chlorine or trifluoromethoxy.3. (canceled)
 4. The liquid crystal composition according to claim 1,wherein the second component is at least one compound selected from thegroup of compounds represented by formula (2-1) to formula (2-3):

wherein R² is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons; X¹ and X² are independentlyhydrogen or fluorine; and Y¹ is fluorine, chlorine or trifluoromethoxy.5. (canceled)
 6. The liquid crystal composition according to claim 1,wherein the ratio of the first component is in the range of 5% by weightto 50% by weight and the ratio of the second component is in the rangeof 5% by weight to 50% by weight, based on the total weight of theliquid crystal composition.
 7. The liquid crystal composition accordingto claim 1, further including at least one compound selected from thegroup of compounds represented by formula (3) as a third component:

wherein R³ and R⁴ are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons, alkenyl having 2 to 12, or alkenyl having 2 to12 carbons in which arbitrary hydrogen is replaced by fluorine; the ringE, the ring F and the ring G are independently 1,4-cyclohexylene,1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z¹ and Z² are independently a single bond,ethylene or carbonyloxy; and m is 0 or
 1. 8. The liquid crystalcomposition according to claim 7, wherein the third component is atleast one compound selected from the group of compounds represented byformula (3-1) to formula (3-6):

wherein R³ and R⁴ are independently alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons, alkenyl having 2 to 12 carbons, or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine. 9-12. (canceled)
 13. The liquid crystal composition accordingto claim 7, wherein the ratio of the third component is in the range of40% by weight to 85% by weight based on the total weight of the liquidcrystal composition.
 14. The liquid crystal composition according toclaim 1, further including at least one compound selected from the groupof compounds represented by formula (4) as a fourth component:

wherein R⁵ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; the ring H is independently1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene or 2,5-pyrimidine; Z³is independently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹ and X² are independently hydrogen or fluorine;Y¹ is fluorine, chlorine or trifluoromethoxy; and o is 1 or
 2. 15. Theliquid crystal composition according to claim 14, wherein the fourthcomponent is at least one compound selected from the group of compoundsrepresented by formula (4-1) to formula (4-12):

wherein R⁵ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons. 16-20. (canceled)
 21. The liquid crystal composition accordingto claim 14, wherein the ratio of the fourth component is in the rangeof 5% by weight to 40% by weight based on the total weight of the liquidcrystal composition.
 22. The liquid crystal composition according toclaim 1, wherein the maximum temperature of a nematic phase is 70° C. orhigher, the optical anisotropy (25° C.) at a wavelength of 589nanometers is 0.08 or more, and the dielectric anisotropy (25° C.) at afrequency of 1 kHz is 2 or more.
 23. A liquid crystal display elementcontaining the liquid crystal composition according to claim
 1. 24. Theliquid crystal display element according to claim 23, wherein anoperating mode of the liquid crystal display element is a TN mode, anOCB mode, an IPS mode or a PSA mode, and a driving mode of the liquidcrystal display element is an active matrix mode.
 25. The liquid crystalcomposition according to claim 7, further including at least onecompound selected from the group of compounds represented by formula (4)as a fourth component:

wherein R⁵ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons or alkenyl having 2 to 12 carbons; the ring H is independently1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene or 2,5-pyrimidine; Z³is independently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹ and X² are independently hydrogen or fluorine;Y¹ is fluorine, chlorine or trifluoromethoxy; and o is 1 or
 2. 26. Theliquid crystal composition according to claim 25, wherein the fourthcomponent is at least one compound selected from the group of compoundsrepresented by formula (4-1) to formula (4-12):

wherein R⁵ is alkyl having 1 to 12 carbons or alkenyl having 2 to 12carbons.
 27. The liquid crystal composition according to claim 25,wherein the ratio of the fourth component is in the range of 5% byweight to 40% by weight based on the total weight of the liquid crystalcomposition.